sdl

SDL_sysmutex.c (5188B)

---

 /*
   Simple DirectMedia Layer
   Copyright (C) 1997-2020 Sam Lantinga <slouken@libsdl.org>
 
   This software is provided 'as-is', without any express or implied
   warranty.  In no event will the authors be held liable for any damages
   arising from the use of this software.
 
   Permission is granted to anyone to use this software for any purpose,
   including commercial applications, and to alter it and redistribute it
   freely, subject to the following restrictions:
 
   1. The origin of this software must not be misrepresented; you must not
      claim that you wrote the original software. If you use this software
      in a product, an acknowledgment in the product documentation would be
      appreciated but is not required.
   2. Altered source versions must be plainly marked as such, and must not be
      misrepresented as being the original software.
   3. This notice may not be removed or altered from any source distribution.
 */
 #include "../../SDL_internal.h"
 
 #include <errno.h>
 #include <pthread.h>
 
 #include "SDL_thread.h"
 
 #if !SDL_THREAD_PTHREAD_RECURSIVE_MUTEX && \
     !SDL_THREAD_PTHREAD_RECURSIVE_MUTEX_NP
 #define FAKE_RECURSIVE_MUTEX 1
 #endif
 
 struct SDL_mutex
 {
     pthread_mutex_t id;
 #if FAKE_RECURSIVE_MUTEX
     int recursive;
     pthread_t owner;
 #endif
 };
 
 SDL_mutex *
 SDL_CreateMutex(void)
 {
     SDL_mutex *mutex;
     pthread_mutexattr_t attr;
 
     /* Allocate the structure */
     mutex = (SDL_mutex *) SDL_calloc(1, sizeof(*mutex));
     if (mutex) {
         pthread_mutexattr_init(&attr);
 #if SDL_THREAD_PTHREAD_RECURSIVE_MUTEX
         pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE);
 #elif SDL_THREAD_PTHREAD_RECURSIVE_MUTEX_NP
         pthread_mutexattr_setkind_np(&attr, PTHREAD_MUTEX_RECURSIVE_NP);
 #else
         /* No extra attributes necessary */
 #endif
         if (pthread_mutex_init(&mutex->id, &attr) != 0) {
             SDL_SetError("pthread_mutex_init() failed");
             SDL_free(mutex);
             mutex = NULL;
         }
     } else {
         SDL_OutOfMemory();
     }
     return (mutex);
 }
 
 void
 SDL_DestroyMutex(SDL_mutex * mutex)
 {
     if (mutex) {
         pthread_mutex_destroy(&mutex->id);
         SDL_free(mutex);
     }
 }
 
 /* Lock the mutex */
 int
 SDL_LockMutex(SDL_mutex * mutex)
 {
 #if FAKE_RECURSIVE_MUTEX
     pthread_t this_thread;
 #endif
 
     if (mutex == NULL) {
         return SDL_SetError("Passed a NULL mutex");
     }
 
 #if FAKE_RECURSIVE_MUTEX
     this_thread = pthread_self();
     if (mutex->owner == this_thread) {
         ++mutex->recursive;
     } else {
         /* The order of operations is important.
            We set the locking thread id after we obtain the lock
            so unlocks from other threads will fail.
          */
         if (pthread_mutex_lock(&mutex->id) == 0) {
             mutex->owner = this_thread;
             mutex->recursive = 0;
         } else {
             return SDL_SetError("pthread_mutex_lock() failed");
         }
     }
 #else
     if (pthread_mutex_lock(&mutex->id) != 0) {
         return SDL_SetError("pthread_mutex_lock() failed");
     }
 #endif
     return 0;
 }
 
 int
 SDL_TryLockMutex(SDL_mutex * mutex)
 {
     int retval;
     int result;
 #if FAKE_RECURSIVE_MUTEX
     pthread_t this_thread;
 #endif
 
     if (mutex == NULL) {
         return SDL_SetError("Passed a NULL mutex");
     }
 
     retval = 0;
 #if FAKE_RECURSIVE_MUTEX
     this_thread = pthread_self();
     if (mutex->owner == this_thread) {
         ++mutex->recursive;
     } else {
         /* The order of operations is important.
          We set the locking thread id after we obtain the lock
          so unlocks from other threads will fail.
          */
         result = pthread_mutex_trylock(&mutex->id);
         if (result == 0) {
             mutex->owner = this_thread;
             mutex->recursive = 0;
         } else if (result == EBUSY) {
             retval = SDL_MUTEX_TIMEDOUT;
         } else {
             retval = SDL_SetError("pthread_mutex_trylock() failed");
         }
     }
 #else
     result = pthread_mutex_trylock(&mutex->id);
     if (result != 0) {
         if (result == EBUSY) {
             retval = SDL_MUTEX_TIMEDOUT;
         } else {
             retval = SDL_SetError("pthread_mutex_trylock() failed");
         }
     }
 #endif
     return retval;
 }
 
 int
 SDL_UnlockMutex(SDL_mutex * mutex)
 {
     if (mutex == NULL) {
         return SDL_SetError("Passed a NULL mutex");
     }
 
 #if FAKE_RECURSIVE_MUTEX
     /* We can only unlock the mutex if we own it */
     if (pthread_self() == mutex->owner) {
         if (mutex->recursive) {
             --mutex->recursive;
         } else {
             /* The order of operations is important.
                First reset the owner so another thread doesn't lock
                the mutex and set the ownership before we reset it,
                then release the lock semaphore.
              */
             mutex->owner = 0;
             pthread_mutex_unlock(&mutex->id);
         }
     } else {
         return SDL_SetError("mutex not owned by this thread");
     }
 
 #else
     if (pthread_mutex_unlock(&mutex->id) != 0) {
         return SDL_SetError("pthread_mutex_unlock() failed");
     }
 #endif /* FAKE_RECURSIVE_MUTEX */
 
     return 0;
 }
 
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